I'd probably put an old-style safety (and old-style safety spring & detent ball) on it.
If you're hunting, you'll need some sling swivels and a sling. I'm assuming here it already has sling studs.
If not, you'll have to install them, which is easier on a wooden stock than a synthetic. Uncle Mike's makes a kit which includes the mag cap with stud and a rear stud that screws in. However, it's tough to get that rear stock drilled just right on a synthetic. If your gun doesn't have sling studs and you really want them, it might be easier to just change out the rear stock on a synthetic gun. Another option is a sling that loops around the barrel on the front and the stock on the back. Never cared much for this option myself, however.
Shotguns don't generally come with a case unless (a) you run up on a promotional, or (b) you're buying a more expensive shotgun. I did once get a nice aluminum hard case with a Remington 870, but that was a promotional that Academy was running several years ago. For a hunting gun, just a decent soft case with a zipper will suffice. Lots easier to tuck the gun behind a truck seat, in a tool box, etc. with a soft case.
+1 on Dave McC's recommended loads and chokes.